A computer network is a collection of interconnected computing devices that exchange data and share resources. In a packet-based network, such as the Internet, the computing devices communicate data by dividing the data into small blocks called packets, which are individually routed across the network from a source device to a destination device. The destination device extracts the data from the packets and assembles the data into its original form. Dividing the data into packets enables the source device to resend only those individual packets that may be lost during transmission.
Certain devices within the network, such as routers, contain control units or routing engines that maintain routing information describing routes through the network. Each route defines a path between locations on the network. Large computer networks, such as the Internet, often include many routers that exchange routing information according to a defined routing protocol, such as the Border Gateway Protocol (BGP). From the routing information, a forwarding engine of the routers generates forwarding information, which is used by the routers to relay packet flows through the network and, more particularly to relay the packet flows to a next hop. Upon receiving an incoming packet, the router examines information within the packet to identify the destination for the packet. Based on the destination, the router forwards the packet in accordance with the forwarding information.
In some cases, a router may fail due to a failure of either the software system running on a routing engine or the underlying hardware of the routing engine. As a result of the failed router, customers of the computer network may lose service and routing information may need to be updated throughout the computer network to establish routes around the failed router. As one solution, a backup routing engine may be used to provide high availability (HA) for the router during operation of the routing functionality by the primary routing engine. In this case, if the primary routing engine of the router fails, the router may perform a graceful restart, e.g., graceful routing engine switchover (GRES), by replicating individual kernel states from the primary routing engine to the backup routing engine.